Music Technology - Apr 1987 Audio-Optics QED

Audio-Optics QED

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Audio-Optics QED

Infra-Red Guitar Pickup

It sounds like sci-fi, but someday, all guitar pickups may work by sensing shadows along the frets with an infrared detector. Rick Davies again.

AS YOU PROBABLY know, this magazine usually reserves In Brief pages for previews of synthesisers, effects, and other electronic devices when we have not had an opportunity to review them in depth, and for reviews of items that can comfortably be covered within the space of a single page. Now we are deviating from this unwritten norm because the QED pickup - an American invention that should, all things being equal, soon be available in the UK as well - is really different, and may well have a lasting effect on the sound of electric guitars.

Many shortcomings of standard magnetic guitar pickups are either overlooked, or so familiar to guitarists that they are considered as part and parcel of just being a guitarist. All guitarists have, at one time or another, had a go at reducing the amount of hum generated by their guitar pickups. But how many guitarists realise the effect the magnetic pickup has on a string's ability to sustain, and the effect this has on the string's overtone series? It would be easy to say that it doesn't matter, that this has always been the case, and that all we can do is work around these drawbacks - were it not for the alternative that the QED pickup presents.

Rather than sensing fluctuations in a magnetic field which a metal string vibrates within, the QED uses two sets of infra-red sensors to detect string vibrations by sensing the shadows cast on the infra-red sensor by the string. The QED uses two sets of sensors for each string, so that the string's vibrations are sensed over two perpendicular axes (ie. back and forth and up and down), something magnetic pickups are incapable of doing. By eliminating the magnetic influence over the string's vibrations, the QED produces a more accurate representation of the string's natural acoustic characteristics, and gives guitarists a much higher dynamic range to work within.

There is another interesting side-effect that could make guitarists take another look at how they amplify and record their instruments in studios and on stage: the QED works equally well with nylon strings as it does with steel strings. Audio Optics made this perfectly clear when they demonstrated a nylon-strung Strat at the NAMM show in February. The sound which came out of Audio Optics' monitor system was not that of a Strat, but that of a nylon-string guitar - without any of the acoustic colouration of a hollow body. And though, for many guitarists, this means that the dream of stringing a guitar with both steel and nylon strings has come true, the real crux of the matter is that the QED works with any strand of material which vibrates. It was almost frightening to see the woofers on Audio Optics' studio monitors moving to and fro as the designers demonstrated their pickup's frequency response by manually moving one string back and forth.

The QED derives power for its sensors from a rackmounting unit which provides individual volume control for each string; since the QED depends on one set of sensors per string, the system automatically has six separate audio outputs and a summed output. The unit also has a six-band EQ for tailoring the summed output, so you have the option of either running the unit in stereo, or running each string output through its own signal-processing.

At NAMM, the QED was demonstrated with each string running through a separate Yamaha SPX90 processor. A slightly less costly approach might be to run the outputs into a Simmons SPM8:2 programmable mixer, which has built-in three-band EQ, auto-pan, LFO modulation, and two effects sends... But then that's just one of many possibilities.

Audio Optics say they plan on supporting the QED in future with various effects and programmable EQ systems designed especially for six-channel pickups, though the basic non-programmable rack is the only unit being prepared for production at the moment.

Initially, Audio Optics will offer the QED as a custom retrofit to any guitar, but plan on shifting the emphasis to their own QED-equipped custom guitars. Christopher Wilcox, designer of the QED, says there are more complications involved in retrofitting guitars with the QED than most guitarists may be aware of. By offering a completely set-up guitar, Audio Optics will reduce the potential for customisation flaws.

But as we all know, sci-fi innovations like these are all very well, except that they come with sci-fi price-tags. Not this one, chum. The retrofit kit should cost in the region of $400 in the States, including the rack unit, and the custom guitar will probably retail for around $1500.

The QED is still at its prototype stage, and a lot could happen between now and production. But rest assured that as a concept, this one is going to make plenty of waves.